Endogenous cytokinin dynamics in micropropagated tulips during bulb formation process influenced by TDZ and iP pretreatment

Polyamines and methyl jasmonate in bulb formation of in vitro propagated tulips

“…Then, its contents declined to the lowest levels at the final bulbing stage (S5), except for cultivar NB, in which Spm increased at this time. This phase in the cultivars easily forming bulbs (FB, P20 and P14) was associated with the commencement of bulb enlargement and the simultaneous development of dormancy manifesting with leaf yellowing, as previously reported for another easy bulbing tulip cultivar 'Prominence' (Podwyszyńska et al 2014). In the cultivar NB, such symptoms were not visible at S5 (6 weeks after the end of cooling).…”

“…3 Contents of endogenous polyamines in the in vitro shoots/ bulbing shoots of the tulip cultivars 'Fringed Black' (FB), 'New Beet' (NB), P14 and P20 during successive micropropagation stages: S1, after 6 weeks of the standard multiplication subculture; S2, at the fifth week of the last multiplication subculture; S3, 5 weeks later-just before cold treatment; S4, at the end of the 13-week-cold treatment; S5, 6 weeks after the end of cold treatment (at the shoot base swelling/bulb formation phase); mean ± SE (n = 4), F and P for ANOVA Phase 9 Cultivar are given for each endogenous polyamine: a putrescine: F = 6.8, P = 0.00, b spermidine: F = 2.6, P = 0.01, c spermine: F = 9.22, P = 0.00 Plant Cell Tiss Organ Cult (2015) 123:591-605 601 ethylene promoted tulip bulb growth in vitro (Podwyszyńska 2006a). Previous investigations revealed that the low bulbing ability and related delayed leaf yellowing of another tulip cultivar 'Blue Parrot' was associated with large CK accumulation during last phase of the bulb formation (Podwyszyńska et al 2014). Rakova and Romanov (2005) based on their studies with seedling of transgenic Arabidopsis indicated that endogenous PAs can significantly modulate an amplitude of a CK primary response gene expression in vivo.…”

“…In the first phase, shoots are prepared for bulbing at the temperature of 18°C. They develop dormancy and become sensitive to low temperature treatment, and their endogenous level of abscisic acid (ABA) increases and level of indole-3-acetic acid (IAA) decreases (Podwyszyńska et al 2004). In the second phase, bulb development is induced by treatment of the shoots with a low temperature of 5°C for 12-14 weeks.…”

“…However, some genotypes have low bulbing capacity under these conditions (Podwyszyńska 2006b;Podwyszyńska et al 2014). Other tulip genotypes, such as the one used for this study, the breeding line P14, produce high numbers of very small bulbs with an average mass below 60 mg.…”

“…Bulbing efficiency was markedly increased by treatments with MeJA at the last phase of this process, 6 weeks after the end of cooling shoots (Podwyszyńska 2006a). Recently, it has been proved that the replacement of thidiazuron (TDZ) (used as standard for shoot multiplication) with isopentenyladenine (iP) in the last multiplication subculture significantly enhanced bulb formation (Podwyszyńska et al 2014). In the case of the cultivar NB, with low bulbing ability, such treatments, however, were found to be insufficient for enhancing the efficiency of this storage organ development.…”